THE HAGUE — Harry van Bommel, a left-wing member of the Dutch Parliament, had persuasive allies in convincing voters that they should reject a trade pact with Ukraine — his special “Ukrainian team,” a gleefully contrarian group of émigrés whose sympathies lay with Russia.

They attended public meetings, appeared on television and used social media to denounce Ukraine’s pro-Western government as a bloodthirsty kleptocracy, unworthy of Dutch support. As Mr. Van Bommel recalled, it “was very handy to show that not all Ukrainians were in favor.”

Handy but also misleading: The most active members of the Ukrainian team were actually from Russia, or from breakaway Russian-speaking regions of Ukraine, and parroted the Kremlin line.

The Dutch referendum, held last April, became a battering ram aimed at the European Union. With turnout low, Dutch voters rejected the trade agreement between the European Union and Ukraine, delighting Moscow, emboldening pro-Russia populists around Europe and leaving political elites aghast.

It is unclear whether the Ukrainian team was directed by Russia or if it was acting out of shared sympathies, and Mr. Van Bommel said he never checked their identities. But Europe’s political establishment, already rattled by Britain’s vote to leave the European Union and the election of President Trump in the United States, is worried that the Netherlands referendum could foreshadow what is to come.

Norway announced this month that Russia-linked hackers had attacked government ministries and a political party. Britain’s defense minister has accused Moscow of “weaponizing disinformation.” German, French and Italian officials have also accused Russia-linked partisans of meddling.

The Netherlands is holding its own national elections on March 15, and domestic intelligence officials say that foreign countries, notably Russia, have tried hundreds of times in recent months to penetrate the computers of government agencies and businesses. Volkskrant, a Dutch newspaper, reported last week that the same two Russian hacking groups that pilfered emails from the Democratic National Committee were among those targeting the Netherlands.

The Dutch interior minister announced that all vote tallies in the March election would be done by hand so as to remove computers from the electoral process and calm fears of hacking by unidentified “state actors.”

“Those in power are very worried — there is more than ample reason for alarm over interference in elections,” said Sijbren de Jong of the Hague Center for Strategic Studies, a research group in The Hague, the seat of the Dutch government. “But the real risk are populists who run, knowingly or unwittingly, with Russia’s agenda because they know it is damaging to the status quo in Europe that they want to destroy. All Russia really needs to do is sit back and let populists do their bidding.”

No one has yet come up with concrete evidence that the Russian state, rather than individual Russians, is working to skew the election, and many wonder why Moscow would even bother trying to do so in a small country with none of the geopolitical heft of the United States or Germany. But Mr. de Jong said the referendum last year showed that “a little effort goes a long way” and could help “destroy the European Union from inside.”

The Netherlands should be difficult terrain for Russia. Last year, the Dutch Safety Board linked Russia to the death of 298 people — including nearly 200 Dutch nationals — in a passenger plane flying from Amsterdam that was shot down in July 2014 over territory held by Russian-armed rebels in eastern Ukraine.

The finding was a public relations disaster for Moscow, and Russian hackers have attacked computers at the Dutch agency, while Russian sympathizers in the Netherlands, including members of Mr. Van Bommel’s Ukrainian team, have labored tirelessly to promote implausible alternative theories for the downing of the Boeing jet carrying Malaysia Airlines Flight 17.

Even Geert Wilders, the country’s anti-Europe, anti-immigrant, anti-establishment firebrand, has kept a distance from Moscow, unlike populist leaders in France and Italy. Yet if Mr. Wilders, whose party is leading in opinion polls, is not an ally, his Euroskeptic agenda dovetails perfectly with the Kremlin’s broader agenda to weaken the European Union and shatter European unity against Russia.

Sico van der Meer, a research fellow at the Netherlands Institute of International Relations, said Russia viewed the West as an adversary and had a clear interest in seeing the election of anti-establishment populists who, no matter what their personal take on Russia, all want to undermine the European Union and, in some cases, NATO.

The Dutch intelligence agency, the AIVD, in a publicly released assessment of Russian activities, agreed that measuring the scale of any state-sponsored Russian interference was extremely difficult, as Moscow’s effort to shape public opinion “takes place in a twilight zone between diplomacy and intelligence.”

But the report also noted that the Netherlands had been targeted as part of a “global campaign to influence policy and perceptions on Russia” and, as part of this effort, Moscow had made use of a “network of contacts built up over the years.”

One such contact is Vladimir Kornilov, a Russian-born historian and political analyst who grew up in eastern Ukraine and now lives in The Hague, where he runs a one-man research outfit called the Center for Eurasian Studies. Emails stolen by a pro-Ukrainian hacking group show how Mr. Kornilov offered information and advice to politicians and others in Moscow during his previous work at a Russian-funded research institute in Kiev.

Before the Dutch referendum last year, Mr. Kornilov campaigned against the Ukraine trade deal, describing himself benignly as “a Ukrainian expat in The Hague” who was “stunned by the seemingly endless stream of lies and propaganda” about Russia and felt obliged to respond.

“After the referendum here, everybody thought this was just a Dutch problem, but now we see it was just the beginning,” Mr. Kornilov said in an interview, denying any financial or other links to the Russian state. “There is a huge crisis in the European Union.”

Nor did he agitate alone. He contacted Mr. Van Bommel as well as Thierry Baudet, the head of a conservative research group, Forum for Democracy, which he has since converted into a political party that takes Russia’s side on a host of issues and is competing for seats in the March election on a platform of hostility to the European Union.

During the referendum campaign, Mr. Baudet posted a Twitter message saying that Ukraine “is not a nation state” and retweeted a false report that Ukrainian soldiers had crucified a 3-year-old Russian-speaking boy in eastern Ukraine. The crucifixion story began with an invented report by Russia’s main state-controlled television channel, which interviewed a supposed Ukrainian witness to the crucifixion who was later identified as a Russian actress.

The bogus crucifixion story circulated through social media and was followed by an even more blatant exercise in fake news, when a video appeared on YouTube that purported to show members of the Azov Battalion, a group of Ukrainian militants, burning the Dutch flag and threatening terrorist attacks if Dutch voters did not support Ukraine.

“All the Kremlin has to do is click like or retweet and then sit back and say ‘thank you,’” said Mr. de Jong, the researcher.

The anonymity of the internet, he added, makes it difficult to distinguish between ordinary people voicing their genuine opinions and state-sponsored trolls. “There is no smoking gun, only lots of smoke,” Mr. de Jong acknowledged.

Mr. Baudet, in an interview in Amsterdam, denied spouting Russia propaganda and said he was merely trying to counter what he called “Europe’s remarkable Russophobia” and to make sure that Russia’s side of the story did not get drowned out.

Ukraine did send officials and activists to the Netherlands to lobby support for a “yes” vote, presenting Ukraine as a victim of Russian aggression. But, unlike some activists on the other side, they openly declared their identities and affiliation.

Michiel Servaes, a Labor Party member of Parliament, campaigned in favor of the pact with Ukraine and said people like Mr. Baudet promoted a narrative that was “word for word what would be used by a spokesman from the Kremlin.” He recalled facing a barrage of criticism at one public meeting from a member of the audience who introduced herself as a Ukrainian but who turned out to be Russian.

For his part, Mr. Van Bommel acknowledged that some of his “Ukrainian” helpers were perhaps Russian but said it was not his job to verify their identities.

“I never ask people to see their passports,” he said during an interview in The Hague. “If they support our political platform they are welcome.”

A particularly active member of the Ukrainian team was Nikita Ananjev, a 26-year-old student born in Moscow who moved with his mother to the Netherlands, where he is now chairman of the Russian Student Association.

He said he had attended 15 or more public meetings across the Netherlands during the referendum campaign, speaking out against the Ukrainian pact and what he described as the European Union’s “rusty and corrupted nomenklatura” and its unfairly negative views of Russia.

Mr. Ananjev, now a university student in the eastern Dutch region of Twente, went to Moscow in 2013 for a “youth leaders school,” a program sponsored by Rossotrudnichestvo, a state-funded organization that promotes cultural exchanges and works to promote Moscow’s take on the world. In December, he visited Brussels for the European Russian Forum, an annual gathering of Moscow-friendly politicians and experts supported by the Russian Foreign Ministry.

Complaining that Russians who defend their country and criticize its adversaries often get labeled unfairly as intelligence operatives, he said in an interview: “I am not a spy. Not yet.”

Correction: February 17, 2017An earlier version of this article referred imprecisely to the areas of Ukraine that some of the members of the “Ukrainian team” were from. They are breakaway Russian-speaking regions, not just Russian-speaking.

Photo: Harry van Bommel, a left-wing member of Parliament, in his office in The Hague. He used a “Ukrainian team” that actually included Russians in an effort to influence a Dutch referendum last year on a trade agreement with Ukraine. Credit Ilvy Njiokiktjien for The New York Times.

The Ministry of Foreign Affairs of Ukraine filed a lawsuit in the UN International Court of Justice against Russia within the framework of the International Convention for the Suppression of the Financing of Terrorism and the International Convention on the Elimination of All Forms of Racial Discrimination, says the site of the Foreign Minister. This is done on the instructions of the President of Ukraine Petro Poroshenko, issued on 16 January.

Alexander Lukashenko on 9 January signed a decree № 8 "On the establishment of visa-free entry and exit of foreign nationals." The document establishes visa-free entry to Belarus for a period not exceeding 5 days at the entrance through the checkpoint "National Airport Minsk" for citizens of 80 countries, - reported the press service of the President of Belarus.